RESUMEN
Interleukin 10 (IL-10) is an antiinflammatory cytokine, but also promotes B cell responses and plays a pathogenic role in systemic lupus erythematosus (SLE). CD4+CCR6+IL-7R+T cells from human tonsils produced IL-10 following stimulation by naïve B cells, which promoted B cell immunoglobulin G (IgG) production. These tonsillar CCR6+B helper T cells were phenotypically distinct from follicular helper T (TFH) cells and lacked BCL6 expression. In peripheral blood, a CCR6+T cell population with similar characteristics was identified, which lacked Th17- and TFH-associated gene signatures and differentiation-associated surface markers. CD4+CCR6+T cells expressing IL-10, but not IL-17, were also detectable in the spleens of cytokine reporter mice. They provided help for IgG production in vivo, and expanded systemically in pristane-induced lupus-like disease. In SLE patients, CD4+CCR6+IL-7R+T cells were associated with the presence of pathogenic anti-dsDNA (double-stranded DNA) antibodies, and provided spontaneous help for autoantibody production ex vivo. Strikingly, IL-10-producing CCR6+T cells were highly abundant in lymph nodes of SLE patients, and colocalized with B cells at the margins of follicles. In conclusion, we identified a previously uncharacterized population of extrafollicular B helper T cells, which produced IL-10 and could play a prominent pathogenic role in SLE.
Asunto(s)
Linfocitos B/inmunología , Interleucina-10/inmunología , Lupus Eritematoso Sistémico/inmunología , Receptores CCR6/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Adulto , Animales , Formación de Anticuerpos , Niño , Citocinas/inmunología , Humanos , Interleucina-10/biosíntesis , Interleucina-17/metabolismo , Lupus Eritematoso Sistémico/metabolismo , Ratones , Ratones Endogámicos C57BL , Tonsila Palatina/citología , Tonsila Palatina/inmunología , Receptores CCR6/biosíntesis , Células Th17/inmunologíaRESUMEN
Systemic lupus erythematosus (SLE) is a highly heterogeneous autoimmune disease characterised by the production of pathogenic autoantibodies against nuclear self-antigens. The anti-inflammatory and tolerogenic cytokine Interleukin-10 appears to play a paradoxical pathogenic role in SLE and is therefore currently therapeutically targeted in clinical trials. It is generally assumed that the pathogenic effect of IL-10 in SLE is due to its growth and differentiation factor activity on autoreactive B-cells, but effects on other cells might also play a role. To date, a unique cellular source of pathogenic IL-10 in SLE has not been identified. In this review, we focus on the contribution of different CD4+T-cell subsets to IL-10 and autoantibody production in SLE. In particular, we discuss that IL-10 produced by different subsets of adaptive regulatory T-cells, follicular helper T-cells and extra-follicular B-helper T-cells is likely to have different effects on autoreactive B-cell responses. A better understanding of the role of IL-10 in B-cell responses and lupus would allow to identify the most promising therapies for individual SLE patients in the future.
Asunto(s)
Interleucina-10/inmunología , Lupus Eritematoso Sistémico/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Linfocitos T Reguladores/inmunología , Animales , Autoanticuerpos/inmunología , Linfocitos B/inmunología , HumanosRESUMEN
Follicular helper T cells (TFHs) are a key component of adaptive immune responses as they help antibody production by B cells. Differentiation and function of TFH cells are controlled by the master gene BCL6, but it is largely unclear how this transcription repressor specifies the TFH program. Here we asked whether BCL6 controlled helper function through down-regulation of specific microRNAs (miRNAs). We first assessed miRNA expression in TFH cells and defined a TFH-specific miRNA signature. We report that hsa-miR-31-5p (miR-31) is down-regulated in TFH; we showed that BCL6 suppresses miR-31 expression by binding to its promoter; and we demonstrated that miR-31 inhibits the expression of molecules that control T-helper function, such as CD40L and SAP. These findings identify a BCL6-initiated inhibitory circuit that stabilizes the follicular helper T cell program at least in part through the control of miRNA transcription. Although BCL6 controls TFH activity in human and mouse, the role of miR-31 is restricted to human TFH cell differentiation, reflecting a species specificity of the miR-31 action. Our findings highlight miR-31 as a possible target to modulate human T cell dependent antibody responses in the settings of infection, vaccination, or immune dysregulation.
Asunto(s)
Linfocitos B/inmunología , Ligando de CD40/genética , MicroARNs/genética , Proteínas Proto-Oncogénicas c-bcl-6/genética , Proteína Asociada a la Molécula de Señalización de la Activación Linfocitaria/genética , Linfocitos T Colaboradores-Inductores/inmunología , Inmunidad Adaptativa , Animales , Linfocitos B/citología , Ligando de CD40/inmunología , Diferenciación Celular , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Redes Reguladoras de Genes , Centro Germinal/citología , Centro Germinal/inmunología , Humanos , Ratones , Ratones Endogámicos C57BL , MicroARNs/inmunología , Cultivo Primario de Células , Regiones Promotoras Genéticas , Unión Proteica , Proteínas Proto-Oncogénicas c-bcl-6/inmunología , Transducción de Señal , Proteína Asociada a la Molécula de Señalización de la Activación Linfocitaria/inmunología , Especificidad de la Especie , Linfocitos T Colaboradores-Inductores/citologíaRESUMEN
Humans are continuously exposed to a high number of diverse pathogens that induce different types of immune responses. Primary pathogen-specific immune responses generate multiple subsets of memory T cells, which provide protection against secondary infections. In recent years, several novel T cell subsets have been identified and have significantly broadened our knowledge about T cell differentiation and the regulation of immune responses. At the same time the rapidly growing number of incompletely characterized T cell subsets has also generated some controversies. We therefore review here the current knowledge on features and functions of human α/ß T cell subsets, focusing on CD4(+) T cells classified according to cytokine production and tissue localization. The principal helper and regulatory T cell subsets can be identified by a limited number of relevant surface markers, which are an integral part of the T cell differentiation programs because they are directly induced by the relevant lineage-defining transcription factors. In vivo occurring human T cell subsets can thus be purified directly ex vivo from relevant tissues for molecular and functional studies, and represent not only an ideal model to study T cell differentiation, but they also offer important clinical opportunities.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Subgrupos de Linfocitos T/inmunología , Animales , Antígenos de Superficie/metabolismo , Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , Citocinas/biosíntesis , Interacciones Huésped-Patógeno/inmunología , Humanos , Inmunofenotipificación , Subgrupos de Linfocitos T/metabolismo , Linfocitos T Colaboradores-Inductores/inmunología , Linfocitos T Colaboradores-Inductores/metabolismo , Linfocitos T Reguladores/inmunología , Linfocitos T Reguladores/metabolismoRESUMEN
Memory T lymphocytes divide in vivo in the absence of antigen maintaining a pool of central memory (T(CM)) and effector memory cells (T(EM)) with distinct effector function and homing capacity. We compared human CD4+ naïve T, T(CM) and T(EM) cells for their capacity to proliferate in response to cytokines, which have been implicated in T cell homeostasis. Interleukin (IL)-7 and IL-15 expanded with very high efficiency T(EM), while T(CM) were less responsive and naïve T cells did not respond at all. Dendritic cell (DC)-derived cytokines allowed naïve T cells to respond selectively to IL-4 and potently boosted the response of T(CM) to IL-7 and IL-15 by increasing the expression of the IL-2/IL-15Rss and the common gamma chain (gamma(c)). The ERK and the p38 MAP kinases were selectively required for TCR and cytokine-driven proliferation, respectively. Importantly, in cytokine-driven cultures T(CM) proliferated and some of the proliferating cells acquired effector function and non-lymphoid tissue homing capacity. Ex vivo BrdU incorporation experiments showed that both T(CM) and T(EM) proliferated under steady state conditions in vivo. Altogether these results provide a plausible mechanism for the maintenance of a polyclonal and functionally diverse repertoire of human CD4+ memory T cells and for a sustained antigen-independent generation of T(EM) from a pool of T(CM) cells.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Citocinas/farmacología , Memoria Inmunológica/inmunología , Animales , Antígenos/inmunología , Diferenciación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Replicación del ADN/efectos de los fármacos , Humanos , Activación de Linfocitos/efectos de los fármacos , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , RatonesRESUMEN
Memory T lymphocytes proliferate in vivo in the absence of antigen maintaining a pool of central memory T cells (T(CM)) and effector memory T cells (T(EM)) with distinct effector function and homing capacity. We compared human CD4(+) naive T, T(CM), and T(EM) cells for their capacity to proliferate in response to cytokines, that have been implicated in T cell homeostasis. Interleukin (IL)-7 and IL-15 expanded with very high efficiency T(EM), while T(CM) were less responsive and naive T cells failed to respond. Dendritic cells (DCs) and DC-derived cytokines allowed naive T cells to proliferate selectively in response to IL-4, and potently boosted the response of T(CM) to IL-7 and IL-15 by increasing the expression of the IL-2/IL-15Rbeta and the common gamma chain (gamma(c)). The extracellular signal regulated kinase and the p38 mitogen-activated protein (MAP) kinases were selectively required for TCR and cytokine-driven proliferation, respectively. Importantly, in cytokine-driven cultures, some of the proliferating T(CM) differentiated to T(EM)-like cells acquiring effector function and switching chemokine receptor expression from CCR7 to CCR5. The sustained antigen-independent generation of T(EM) from a pool of T(CM) cells provides a plausible mechanism for the maintenance of a polyclonal and functionally diverse repertoire of human CD4(+) memory T cells.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Diferenciación Celular/inmunología , Citocinas/inmunología , Subgrupos de Linfocitos T/inmunología , Linfocitos T CD4-Positivos/citología , Diferenciación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , División Celular/inmunología , Citocinas/farmacología , Humanos , Memoria Inmunológica , Subgrupos de Linfocitos T/citologíaAsunto(s)
Memoria Inmunológica , Receptores de Quimiocina/biosíntesis , Subgrupos de Linfocitos T/inmunología , Antígenos de Diferenciación de Linfocitos T , Linfocitos T CD4-Positivos/citología , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/citología , Linfocitos T CD8-positivos/inmunología , Diferenciación Celular , Receptores CCR7 , Subgrupos de Linfocitos T/citologíaRESUMEN
Integrin adhesion receptors transduce signals that control complex cell functions which require the regulation of gene expression, such as proliferation, differentiation and survival. Their intracellular domain has no catalytic function, indicating that interaction with other transducing molecules is crucial for integrin-mediated signalling. Here we have identified a protein that interacts with the cytoplasmic domain of the beta2 subunit of the alphaL/beta2 integrin LFA-1. This protein is JAB1 (Jun activation domain-binding protein 1), a coactivator of the c-Jun transcription factor. We found that JAB1 is present both in the nucleus and in the cytoplasm of cells and that a fraction of JAB1 colocalizes with LFA-1 at the cell membrane. LFA-1 engagement is followed by an increase of the nuclear pool of JAB1, paralleled by enhanced binding of c-Jun-containing AP-1 complexes to their DNA consensus site and increased transactivation of an AP-1-dependent promoter. We suggest that signalling through the LFA-1 integrin may affect c-Jun-driven transcription by regulating JAB1 nuclear localization. This represents a new pathway for integrin-dependent modulation of gene expression.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Antígeno-1 Asociado a Función de Linfocito/metabolismo , Factor de Transcripción AP-1/metabolismo , Factores de Transcripción/metabolismo , Animales , Anticuerpos Monoclonales/metabolismo , Complejo del Señalosoma COP9 , Células COS , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Regulación de la Expresión Génica/fisiología , Humanos , Péptidos y Proteínas de Señalización Intracelular , Células Jurkat , Luciferasas/genética , Péptido Hidrolasas , Unión Proteica , Agregación de Receptores , Transducción de Señal , Linfocitos T/metabolismo , Transcripción GenéticaRESUMEN
In clinical transplantation, the occurrence of cyclosporin A (CsA)-resistant production of IL-2 in vitro correlates with graft rejection in vivo. In this study we investigated the role of the costimulatory molecules CD28 and LFA-1 in this process in the setting of TCR-induced proliferation of primary T lymphocytes in vitro. Co-stimulation with ICAM-1 and B7.2 led to strong and CsA-resistant proliferation, which was found to be largely IL-2 dependent. All of the known calcineurin-dependent events, such as induction of NF-AT and NF-kappaB or stress-activated protein kinase activation, were markedly modulated by CsA independently of costimulation. In contrast, both ICAM-1 and B7.2 enhanced the half-life of the inducible IL-2 transcript in a CsA-resistant manner. LFA-1- but not CD28-induced IL-2 mRNA stabilization required the integrity of the actin-based cytoskeleton, suggesting that the two costimulatory molecules impact on qualitatively different signaling pathways. This is further suggested by the demonstration that LFA-1 and CD28 acted synergistically to confer CsA resistance in a model of co-stimulation using superantigen-pulsed dendritic cells. We propose that IL-2 transcript accumulation and subsequent T cell proliferation at the low transcriptional rate imposed by CsA are the result of co-stimulation-dependent stabilization of IL-2 mRNA.
Asunto(s)
Antígenos CD28/inmunología , Ciclosporina/farmacología , Interleucina-2/genética , Antígeno-1 Asociado a Función de Linfocito/inmunología , Proteínas Nucleares , Estabilidad del ARN/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Linfocitos T/efectos de los fármacos , Antígenos CD/inmunología , Antígeno B7-2 , Calcineurina/fisiología , Células Cultivadas , Citoesqueleto/metabolismo , Proteínas de Unión al ADN/metabolismo , Células Dendríticas/inmunología , Sinergismo Farmacológico , Humanos , Molécula 1 de Adhesión Intercelular/inmunología , Interleucina-2/biosíntesis , Interleucina-2/inmunología , Activación de Linfocitos/efectos de los fármacos , Glicoproteínas de Membrana/inmunología , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Proteínas Quinasas Activadas por Mitógenos/metabolismo , FN-kappa B/metabolismo , Factores de Transcripción NFATC , Regiones Promotoras Genéticas/genética , Unión Proteica/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Superantígenos/inmunología , Linfocitos T/citología , Linfocitos T/inmunología , Linfocitos T/metabolismo , Factores de Transcripción/metabolismoRESUMEN
Th1 and Th2 cells are functionally distinct subsets of CD4+ T lymphocytes whose tissue-specific homing to sites of inflammation is regulated in part by the differential expression of P- and E-selectin ligands and selected chemokine receptors. Here we investigated the expression and function of beta 1 integrins in Th1 and Th2 cells polarized in vitro. Th1 lymphocytes adhere transiently to the extracellular matrix ligands laminin 1 and fibronectin in response to chemokines such as RANTES and stromal cell-derived factor-1, and this process is paralleled by the activation of the Rac1 GTPase and by a rapid burst of actin polymerization. Selective inhibitors of phosphoinositide-3 kinase prevent efficiently all of the above processes, whereas the protein kinase C inhibitor bisindolylmaleimide prevents chemokine-induced adhesion without affecting Rac1 activation and actin polymerization. Notably, chemokine-induced adhesion to beta 1 integrin ligands is markedly reduced in Th2 cells. Such a defect cannot be explained by a reduced sensitivity to chemokine stimulation in this T cell subset, nor by a defective activation of the signaling cascade involving phosphoinositide-3 kinase, Rac1, and actin turnover, as all these processes are activated at comparable levels by chemokines in the two subsets. We propose that reduced beta 1 integrin-mediated adhesion in Th2 cells may restrain their ability to invade and/or reside in sites of chronic inflammation, which are characterized by thickening of basement membranes and extensive fibrosis, requiring efficient interaction with organized extracellular matrices.
Asunto(s)
Quimiocina CCL5/fisiología , Quimiocinas CXC/fisiología , Integrina beta1/fisiología , Células Th2/inmunología , Regulación hacia Arriba/inmunología , Actinas/metabolismo , Biopolímeros/metabolismo , Antígenos CD18/biosíntesis , Calcio/metabolismo , Adhesión Celular/inmunología , Quimiocina CXCL12 , Proteínas de la Matriz Extracelular/metabolismo , Fibronectinas/metabolismo , Humanos , Integrina alfa6beta1 , Integrina beta1/biosíntesis , Integrinas/metabolismo , Líquido Intracelular/metabolismo , Laminina/metabolismo , Unión Proteica/inmunología , Receptores de Laminina/metabolismo , Transducción de Señal/inmunología , Células TH1/inmunología , Células TH1/metabolismo , Células Th2/metabolismoRESUMEN
The 8B4/20 Ag is a 120-kDa molecule whose expression on human thymocytes varies according to the differentiation stage: high density on immature CD3-/low thymocytes, reduced density on CD3medium and double-positive thymocytes, and absent on CD3high and single-positive thymocytes and on circulating T cells. In this paper we present immunological and biochemical evidence demonstrating that 8B4/20 Ag is a variant of CD43. We show that 8B4/20-expressing molecules, which are a subset of the CD43 molecules on thymocytes, are heterogeneous in charge, suggesting varying sialylation levels. The 8B4/20 epitope was mapped to the peripherally exposed N-terminal region of CD43, and the 8B4/20 antigenic determinant was characterized by requirement for the sialic acid exocyclic polyhydroxyl side chain, a feature shared with ligands of CD22. Altogether, 8B4/20-CD43 expression pattern and biochemical characteristics suggest its participation in carbohydrate-based interactions in the thymus. We therefore used specific Ab to mimic putative 8B4/20 interactions with natural ligand and examined the effect on isolated thymocytes. Treatment with 8B4/20 had no effect on in vitro apoptosis of isolated thymocytes. In contrast, 8B4/20 ligation enhanced the conversion of isolated thymocytes to differentiated phenotypes. Increased numbers were found in 8B4/20-treated cultures of CD3high and single-positive thymocytes and decreased numbers of CD3-/low and double-positive thymocytes, strongly suggesting that engagement of 8B4/20 delivers a positive signal that favors completion of the thymocyte maturation program. The ability of 8B4/20 mAb to drive thymocyte maturation in vitro suggests that CD43 molecules bearing the 8B4/20 epitope participate in early events of thymic selection.
Asunto(s)
Antígenos CD/inmunología , Epítopos de Linfocito T/inmunología , Sialoglicoproteínas/inmunología , Timo/citología , Anticuerpos Monoclonales , Especificidad de Anticuerpos , Variación Antigénica , Apoptosis , Diferenciación Celular , Separación Celular , Mapeo Epitopo , Humanos , Leucosialina , Subgrupos Linfocitarios/inmunología , Timo/inmunologíaRESUMEN
Anchorage dependence defines the cellular requirement for integrin-mediated adhesion to substrate to initiate DNA replication in response to growth factors. In this study we investigated whether normal T cells, which spend extended periods in a nonadherent state, show similar requirements for cell cycle progression in response to TCR stimulation. Resting primary T lymphocytes were induced to enter the cell cycle by TCR triggering, and leukocyte integrins were either engaged using purified ICAM-1 or inhibited with function-blocking mAbs. Our data indicate that leukocyte integrins complement TCR-driven mitogenic signals not as a result of their direct clustering but, rather, via integrin-dependent organization of the actin cytoskeleton. Leukocyte integrin-dependent reorganization of the actin cytoskeleton cooperates with the TCR to effect mitogen-activated protein kinase activation, but also represents a required late (4-8 h poststimulation) component in the mitogenic response of normal T cells. Prolonged leukocyte integrin-dependent spreading, in the context of intercellular contact, is a requisite for the production of the mitogenic cytokine IL-2, which, in turn, is involved in the induction of D3 cyclin and is primarily responsible for the decrease in the cyclin-dependent kinase inhibitor p27kip, resulting in retinoblastoma protein inactivation and S phase entry. Thus, T lymphocytes represent a peculiar case of anchorage dependence, in which signals conveyed by integrins act sequentially with the activating stimulus to effect a sustained production of the essential mitogenic cytokine.